Toxoplasmosis is a serious disease in congenitally infected infants and in immunocompromised patients. Millions of dollars are needed each year to care for victims of congenital toxoplasmosis in the United States alone, and toxoplasmic encephalitis is now the most commonly recognized cause of opportunistic infection of the central nervous system in patients with AIDS. Toxoplasma gondii, a parasite with worldwide distribution, is also a pathogen of significant economic importance in sheep and swine where it causes abortion. Artemisinin (Qinghaosu) and certain derivatives have shown significant antiparasitic activity for the related diseases malaria and toxoplasmosis. Expanded evaluation of other functional derivatives and correlation of results to pharmacological factors leading to high efficacy and low toxicity is a necessary step toward commercialization of an effective agent. The immediate proposal will focus on functional derivatives of Artemisinin at the C-12 position which will be chemically synthesized and evaluated for inhibition of growth of Toxoplasma gondii by published methods. The proposers have a supply of Artemisinin on-hand for starting material, have successfully synthesized other derivatives, have published inhibition studies on T. gondii, and have the necessary technical background to interpret the results as precedence for further research and commercialization.